Substrate processing method and apparatus

ABSTRACT

There is provided a substrate processing method and apparatus which can measure and monitor thickness and/or properties of a film formed on a substrate as needed, and quickly correct a deviation in process conditions, and which can therefore stably provide a product of constant quality. A substrate processing method for processing a substrate having a metal and an insulating material exposed on its surface in such a manner that a film thickness of the metal, with an exposed surface of the metal as a reference plane, is selectively or preferentially changed, including measuring a change in the film thickness and/or a film property of the metal during and/or immediately after processing, and monitoring processing and adjusting processing conditions based on results of this measurement.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a substrate processing method and apparatus,and more particularly to a substrate processing method and apparatus forprotecting interconnects by selectively covering exposed surfaces ofembedded interconnects, which have been formed by embedding an electricconductor such as copper in a surface of a substrate such as asemiconductor wafer, with a coating film (protective film) of a metal oran alloy.

The present invention also relates to a substrate processing method andapparatus for caving in exposed surfaces of embedded interconnects toform recesses, preparatory to selectively covering exposed surfaces ofthe embedded interconnects, which have been formed by embedding anelectric conductor such as copper in a surface of a substrate such as asemiconductor wafer, with a coating film (protective film) of a metal oran alloy.

. Description of the Related Art

As a process for forming interconnects in a semiconductor device, aso-called “damascene process”, which comprises embedding a metal(electric conductor) into interconnect trenches and contact holes, iscoming into practical use. According to this process, aluminum, or morerecently a metal such as silver or copper, is embedded into interconnecttrenches and contact holes previously formed in an interlevel dielectricof a semiconductor substrate. Thereafter, an extra metal is removed bychemical mechanical polishing (CMP) so as to flatten a surface of thesubstrate.

In a case of interconnects formed by such a process, for example, copperinterconnects are formed by using copper as an interconnect material,and embedded copper interconnects have an exposed surface afterflattening processing. In order to prevent thermal diffusion of suchinterconnects (copper), or to prevent oxidation of such interconnects(copper) or to improve electromigration (EM) properties by enhacingadhesion, e.g. in forming thereon an insulating film (oxide film) underan oxidizing atmosphere to produce a semiconductor device having amulti-layer interconnect structure, it is now under study to selectivelycover exposed surfaces of interconnects with a coating film (capmaterial) composed of a Co alloy, a Ni alloy or the like so as toprevent thermal diffusion and oxidation of the interconnects. Such afilm of a Co alloy, a Ni alloy or the like can be produced e.g. byelectroless plating. Further, in order to form a flat coating film onthe exposed surfaces of interconnects, a processing method is beingstudied which comprises caving in the exposed surfaces of embeddedinterconnects to form recesses. The recesses may be formed, for example,by etching or wet polishing.

Consider now an example of selective formation of a coating film(protective film) as illustrated in FIG. 1. In particular, fineinterconnect recesses 4 are first formed in an insulating film 2 of e.g.SiO₂, SiCO, SiOF, or an inorganic or organic low-k material, depositedon a surface of a substrate W, such as a semiconductor wafer. Afterforming a barrier layer 6 of TaN or the like on an entire surface,copper plating, for example, is performed to form a copper film on asurface (barrier layer 6) of the substrate W so that the recesses 4 arefilled with copper. Thereafter, the surface of the substrate W isflattened by CMP (chemical-mechanical polishing), thereby forminginterconnects 8 composed of copper film in the insulating film 2. Acoating film (cap material) 9 of a Co—W—P alloy is formed, e.g. byelectroless plating, selectively on surfaces of interconnects (copperfilm) 8 to protect interconnects 8.

In the above case, the interconnects 8 of metal (copper) and theinsulating film 2 of insulating material are exposed on the surface ofthe substrate W, and it is necessary to selectively form the coatingfilm 9 only on the exposed surfaces of the interconnects 8. When thecoating film 9 is selectively formed only on the exposed surfaces of theinterconnects 8, which are formed in a pattern of long narrow linesseparated from each other by the insulating film 2, the coating film 9will take the form of a number of separate discontinuous films and filmproperties are likely to vary. It is therefore required to control thecoating film 9 so that film thickness and/or film properties areconstant.

When forming the coating film 9 such that its surface is flush with thesurface of the insulating film 2, as shown in FIG. 2, it is necessary tocave in the surfaces of the interconnects 8 to form recesses 8 apreparatory to the formation of coating film 9. In this case, inaddition to control of the thickness of the coating film 9, it isnecessary to precisely control a depth of the recesses 8 a formed abovethe interconnects 8.

SUMMARY OF THE INVENTION

For a continuous thin film formed over a surface of a semiconductorsubstrate, for example, it is possible to measure thickness orproperties of the film by using a common optical or electricresistance-type sensor. For the above-described discontinuous filmselectively covering interconnects or to be cut, however, measurement ofthe film with a conventional sensor is difficult, and it is required toquickly measure the thickness or properties of such a film in anon-destructive manner. In this connection, it is possible at present toprepare a calibration curve in advance by using a destructivemeasurement method, such as TEM (transmission electron microscopy), andperform processing while maintaining process conditions based on thecalibration curve. This method, however, is not practicable in view ofcost and time involved.

Further, in some instances, a method is utilized in which a pilot waferwith a simulated structure of an intended measurement portion issubjected to the same processing and the film thickness or propertiesare measured indirectly, and results of this measurement are utilized tocontrol an actual process. It is, however, not generally practiced toperform a direct measurement on a substrate formed device as aprocessing object for adjustment of the process conditions, and thelike. Wet processings, such as plating, etching and electrolyticpolishing, often use a liquid chemical comprising a number of chemicalcomponents, and it is difficult to monitor and control with accuracy allthe components in the liquid chemical. Further, in processing of a filmon discontinuous exposed metal surfaces, the film thickness orproperties may vary with location depending upon differences in a sizeor an initial state of the exposed surfaces. There is, therefore, adesire to maintain conditions of apparatus and liquid chemical, anddirectly monitor and control a film being processed or to be processedso that a high-quality film processing can be effected.

The present invention has been made in view of the above situation inthe related art. It is therefore an object of the present invention toprovide a substrate processing method and apparatus which can measureand monitor a thickness and/or properties of a film formed on asubstrate as needed, and quickly correct a deviation in processconditions, and which can therefore stably provide a product of constantquality.

In order to achieve this object, the present invention provides asubstrate processing method for processing a substrate having a metaland an insulating material exposed on its surface in such a manner thatfilm thickness of a metal portion, with an exposed surface of the metalas a reference plane, is selectively or preferentially changed,comprising: measuring a change in the film thickness and/or a filmproperty of the metal portion during and/or immediately afterprocessing; and monitoring processing and adjusting processingconditions based on results of this measurement.

According to the substrate processing method, a film thickness and/orfilm property of a processed film is measured during and/or afterprocessing, and a film thickness and/or film property is controlled.Thus, the method enables direct measurement and control on a devicesubstrate. This ensures quality of the film even when the film thicknessor property has changed with time after continued film processing, andmakes it possible to provide a stable product.

The processing may be film formation which increases the film thicknessof the metal portion or film formation in which a different material issuperimposed on the metal.

Alternatively, the processing may be etching or heat processing whichdecreases the film thickness of the metal portion.

In a preferred embodiment of the present invention, measurement of achange in the film thickness and/or the film property of the metalportion is performed on a particular measurement area by using anoptical sensor which is orientable to any point on the substrate. Bysetting a particular area at the same position on each substrate as acontrol target, variations in quality between substrates can beprevented.

In a preferred embodiment of the present invention, measurement of achange in the film thickness and/or the film property of the metalportion is performed on a plurality of measurement areas simultaneouslyor sequentially by using an optical sensor which is orientable to anypoint on the substrate. By setting a plurality of areas on a substrateas control targets, variations in quality in the substrate can beprevented.

The optical sensor may be one which utilizes spectroreflectometry,ellipsometry or spectroscopic ellipsometry. With such an optical sensor,measurement can be performed in a non-destructive manner, i.e. withoutdestroying a substrate, and in a short time of about several seconds toseveral tens of seconds for one measurement area. This is desirable inlight of quality control.

The optical sensor may also be one which utilizes X-ray reflectance,grazing-incidence fluorescent X-rays or a plurality of laserinterferometers. Such an optical sensor enables real-time measurement ofa change in the film thickness and/or the film property of a film beingprocessed (measurement object) in air or in a liquid.

The present invention also provides a substrate processing method forprocessing a substrate having a metal and an insulating material exposedon its surface in such a manner that film thickness of a metal portion,with an exposed surface of the metal as a reference plane, isselectively or preferentially changed, comprising: setting on thesubstrate a measurement area, in which measurement of a change in thefilm thickness of the metal portion is possible, and a target area as acontrol target; preparing a calibration curve showing a relationshipbetween a change in the film thickness of the metal portion in themeasurement area and a change in a film thickness of the metal portionin the target area; measuring the film thickness in the measurement areaduring and/or immediately after processing; and converting this measuredvalue to the film thickness of the metal portion in the target area byusing the calibration curve to monitor and adjust a change in the filmthickness.

Take film formation on exposed surfaces of interconnects for example.When selectively covering the exposed surfaces of interconnects with acoating film (protective film), device performance is generally governedprimarily by a coating film (protective film) formed on theinterconnects. Accordingly, it is most important to control propertiesof the coating film formed on the interconnects. It is, however,difficult to directly measure a film thickness of the coating film onthe interconnects, because the interconnects generally have a width ofnot more than 1 μm. Even with a continuous coating film having arelatively wide area, film properties may vary at various portionsdepending upon sizes. According to the above substrate processingmethod, therefore, a measurement area in which measurement of the filmthickness of e.g. a coating film is possible and a target area as acontrol target are set on a substrate, the film thickness of the coatingfilm formed in the measurement area is measured, and this measured valueis converted to the film thickness of the coating film in the targetarea by using a prepared calibration curve showing a relationshipbetween the film thickness of the coating film in the measurement areaand the film thickness of the coating film in the target area. Thismakes it possible to indirectly determine the film thickness of acoating film, whose measurement is generally impossible, formed oninterconnects.

Also in a case of cutting a coating film (protective film) formed onexposed surfaces of interconnects, a decrease in film thickness can bedetermined indirectly in the same manner as described above.

In a preferred embodiment of the present invention, the film thicknessof the metal portion is measured by an optical sensor, and themeasurement area is sufficiently larger for measurement than a spot sizeof an optical beam emitted from the optical sensor.

In measurement of the film thickness by an optical film thickness sensor(optical sensor), a spot size of a sensor beam, after narrowing thebeam, is generally from several μm to several tens of μm. On the otherhand, a width of interconnects is generally not more than 1 μm asdescrbed above. Accordingly, when attempting to directly measure thefilm thickness of a coating film formed on interconnects, thismeasurement is influenced by an adjacent insulating film (insulatingmaterial) whose surface is exposed. This will produce a largemeasurement error and, in some cases, make measurement impossible. Bysetting (selecting) a measurement area which has a larger size than aspot size of a narrowed optical beam from the optical sensor and onwhich a continuous film is to be formed, it becomes possible to measurethe film thickness of a film formed on the substrate without beinginfluenced by an insulating film (insulating material). Such ameasurement area can be set at a desired position on a substrate. Incase there is no proper measurement area on a substrate, it can be dealtwith by making a dummy pattern.

The present invention also provides a substrate processing method forprocessing a substrate having a metal and an insulating material exposedon its surface in such a manner that a coating film is formedselectively on an exposed surface of the metal, comprising: setting onthe substrate a measurement area, in which measurement of a filmproperty of the coating film is possible, and a target area as a controltarget; preparing a calibration curve showing a relationship between afilm property of the coating film in the measurement area and the filmproperty of the coating film in the target area; measuring the filmproperty in the measurement area during and/or immediately afterformation of the coating film; and converting this measured value to thefilm property of the coating film in the target area by using thecalibration curve to monitor and adjust formation of the coating film.

As with the above-described case of measuring the film thickness of acoating film, film properties of a coating film formed on interconnects,whose measurement is generally impossible, can be determined in anindirect manner according to the present substrate processing method.

The film property of the coating film may be at least one of filmcomposition, density, refractive index, surface roughness, reflectanceand interface width.

In a preferred embodiment of the present invention, the film property ofthe coating film is measured by an optical sensor, and the measurementarea is sufficiently larger than the spot size of an optical beamemitted from the optical sensor.

The present invention further provides a substrate processing apparatuscomprising: a plating unit for plating a substrate having a metal and aninsulating material exposed on its surface in such a manner that acoating film is formed selectively on an exposed surface of the metal; asensor for measuring film thickness and/or a film property of thecoating film during and/or immediately after formation of the coatingfilm; and a control section for controlling the plating unit based on anoutput from the sensor.

The present invention further provides a substrate processing apparatuscomprising: an etching unit for etching a substrate having a metal andan insulating material exposed on its surface in such a manner that anexposed surface of the metal is selectively removed; a sensor formeasuring a decrease in film thickness of a metal portion during and/orimmediately after removal processing of the metal portion; and a controlsection for controlling the etching unit based on an output from thesensor.

The present invention further provides a substrate processing apparatuscomprising: a polishing unit for polishing a substrate having a metaland an insulating material exposed on its surface in such a manner thatan exposed surface of the metal is selectively removed; a sensor formeasuring a decrease in film thickness of a metal portion during and/orimmediately after removal processing of the metal portion; and a controlsection for controlling the polishing unit based on an output from thesensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram illustrating an example of formationof a coating film on interconnects by electroless plating;

FIG. 2 is a cross-sectional diagram illustrating another example offormation of a coating film on interconnects by electroless plating;

FIG. 3 is a layout plan of a substrate processing apparatus according toan embodiment of the present invention;

FIG. 4 is a flow chart of a plating process performed by the substrateprocessing apparatus shown in FIG. 3;

FIG. 5 is a front view showing a pre-treatment unit upon transfer of asubstrate;

FIG. 6 is a front view showing the pre-treatment unit upon chemicaltreatment;

FIG. 7 is a front view showing the pre-treatment unit upon rinsing;

FIG. 8 is a cross-sectional view showing a processing head of thepre-treatment unit upon transfer of a substrate;

FIG. 9 is an enlarged view of portion A of FIG. 8;

FIG. 10 is a view corresponding to FIG. 9, showing the processing headupon fixing of a substrate;

FIG. 11 is a diagram illustrating a system of the pre-treatment unit;

FIG. 12 is a cross-sectional view showing a substrate head of anelectroless plating unit upon transfer of a substrate;

FIG. 13 is an enlarged view of portion B of FIG. 12;

FIG. 14 is a view corresponding to FIG. 13, showing the substrate headof the electroless plating unit upon fixing of a substrate;

FIG. 15 is a view corresponding to FIG. 13, showing the substrate headof the electroless plating unit upon plating;

FIG. 16 is a partially sectional front view showing a plating tank ofthe electroless plating unit when a plating tank cover is closed;

FIG. 17 is a cross-sectional view of a cleaning tank of the electrolessplating unit;

FIG. 18 is a diagram illustrating a system of the electroless platingunit;

FIG. 19 is a vertical sectional front view of a post-treatment/dryingunit;

FIG. 20 is a plan view of a post-treatment/drying unit;

FIG. 21A is a diagram illustrating a relationship between a substrateand regions each defining a chip, and FIG. 21B is a diagram illustratinga relationship between a measurement area and a target area in a regiondefining a chip;

FIG. 22 is a calibration curve showing a relationship between a filmthickness in a measurement area and a film thickness in a target area;and

FIG. 23 is a calibration curve showing a relationship between a filmproperty in a measurement area and a film property in a target area.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail with reference to the drawings.

FIG. 3 shows a layout plan of a substrate processing apparatus accordingto an embodiment of the present invention. As shown in FIG. 3, thesubstrate processing apparatus includes a loading/unloading unit 12housing a substrate cassette 10 that houses substrates W each havinginterconnects 8 of e.g. copper formed in interconnect recesses 4 whichare formed in a surface (see FIG. 1). Along one long side of arectangular housing 16 provided with a ventilation system, there aredisposed in series a first pre-treatment unit 18 for performing cleaningof the surface of a substrate W as a pre-plating treatment, a secondpre-treatment unit 20 for imparting a catalyst to exposed surfaces ofinterconnects 8 after cleaning to activate surfaces of interconnects, anelectroless plating unit 22 for performing electroless plating of thesurface (processing surface) of the substrate W, and a post-treatmentunit 24 for performing a post-plating treatment of the substrate W toenhance selectivity of a coating film (protective film) 9 (see FIG. 1)which has been formed by the electroless plating on the surfaces of theinterconnects 8.

Further, along another long side of the housing 16 are disposed inseries a drying unit 26 for drying the substrate W after post-treatment,a heat treatment unit 28 for heat treating (annealing) the substrate Wafter drying, and a measurement unit 30 provided with a film thicknesssensor 30 a for measuring a film thickness of the coating film(protective film) 9 formed on the surfaces of the interconnects 8 andwith a film property sensor 30 b for measuring a film property of thecoating film 9. Further, a transport robot 34, which is movable on arail 32 parallel to the long sides of the housing 16 and transfers asubstrate between it and each unit or the substrate cassette 10 set inthe loading/unloading unit 12, is disposed centrally between these twolines of units. Output signals from the film thickness sensor 30 a andthe film property sensor 30 b are inputted into a control section 36,and the units, the transport robot and a chemical supply control unit 38are controlled by output signals from the control section 36.

The housing 16 is light-shielded so as to inhibit transmissiontherethrough of external light. This prevents migration of electrons,due to an excitation effect of light, in devices and interconnectsformed in a device surface of a substrate during processing, thuspreventing damage to the devices in the substrate.

Details of the various units provided in the substrate processingapparatus shown in FIG. 3 will now be described.

The first pre-treatment unit 18 and the second pre-treatment unit 20both employ the same two-liquid separation system for preventing mixingof two liquids though processing liquids (liquid chemicals) used aredifferent. These units each hold a substrate W, which has beentransported face down thereto, by sealing a peripheral portion of alower surface, which is a processing surface (front surface), andpressing on a back surface.

As shown in FIGS. 5 to 8, the pre-treatment unit 18, 20 each includes afixed frame 52 that is mounted on an upper part of a frame 50, and amovable frame 54 that moves up and down relative to the fixed frame 52.A processing head 60, which includes a bottomed cylindrical housingportion 56, opening downwardly, and a substrate holder 58, is suspendedfrom and supported by the movable frame 54. In particular, a servomotor62 for rotating the head is mounted to the movable frame 54, and thehousing portion 56 of the processing head 60 is coupled to a lower endof a downward-extending output shaft (hollow shaft) 64 of the servomotor62.

As shown in FIG. 8, a vertical shaft 68, which rotates together with theoutput shaft 64 via a spline 66, is inserted in the output shaft 64, andthe substrate holder 58 of the processing head 60 is coupled to a lowerend of the vertical shaft 68 via a ball joint 70. The substrate holder58 is positioned within the housing portion 56. An upper end of thevertical shaft 68 is coupled via a bearing 72 and a bracket to a fixedring-elevating cylinder 74 secured to the movable frame 54. Thus, byactuation of the cylinder 74, the vertical shaft 68 moves verticallyindependently of the output shaft 64.

Linear guides 76, which extend vertically and guide vertical movement ofthe movable frame 54, are mounted to the fixed frame 52, so that byactuation of a head-elevating cylinder (not shown), the movable frame 54moves vertically by guidance of the linear guides 76.

Substrate insertion windows 56 a for inserting the substrate W into thehousing portion 56 are formed in a circumferential wall of the housingportion 56 of the processing head 60. Further, as shown in FIGS. 9 and10, a seal ring 84 a is provided in a lower portion of the housingportion 56 of the processing head 60, with an outer peripheral portionof the seal ring 84 a being sandwiched between a main frame 80 made ofe.g. PEEK and a guide frame 82 made of e.g. polyethylene. The seal ring84 a is provided to make contact with a peripheral portion of the lowersurface of the substrate W to seal the peripheral portion.

On the other hand, a substrate fixing ring 86 is fixed to a peripheralportion of a lower surface of the substrate holder 58. A columnar pusher90 protrudes downwardly from a lower surface of the substrate fixingring 86 by an elastic force of a spring 88 disposed within the substratefixing ring 86 of the substrate holder 58. Further, a flexiblecylindrical bellows-like plate 92 made of e.g. Teflon (registeredtrademark) is disposed between an upper surface of the substrate holder58 and an upper wall of the housing portion 56 to hermetically sealtherein.

When the substrate holder 58 is in a raised position, a substrate W isinserted from the substrate insertion window 56 a into the housingportion 56. The substrate W is then guided by a tapered surface 82 aprovided on an inner circumferential surface of the guide frame 82, andpositioned and placed at a predetermined position on an upper surface ofthe seal ring 84 a. In this state, the substrate holder 58 is lowered soas to bring the pushers 90 of the substrate fixing ring 86 into contactwith the upper surface of the substrate W. The substrate holder 58 isfurther lowered so as to press the substrate W downwardly by the elasticforce of the springs 88, thereby forcing the seal ring 84 a to makepressure contact with a peripheral portion of the front surface (lowersurface) of the substrate W to seal the peripheral portion while nippingthe substrate W between the housing portion 56 and the substrate holder58 to hold the substrate W.

When head-rotating servomotor 62 is driven while the substrate W is thusheld by the substrate holder 58, the output shaft 64 and the verticalshaft 68 inserted in the output shaft 64 rotate together via the spline66, whereby the substrate holder 58 rotates together with the housingportion 56.

At a position below the processing head 60, there is provided anupward-open treatment tank 100 comprising an outer tank 100 a and aninner tank 100 b (shown in FIG. 11) that have a slightly larger innerdiameter than an outer diameter of the processing head 60. A pair of legportions 104, which is mounted to a lid 102, is rotatably supported onan outer circumferential portion of the treatment tank 100. Further, acrank 106 is integrally coupled to each leg portion 106, and a free endof the crank 106 is rotatably coupled to a rod 110 of a lid-movingcylinder 108. Thus, by actuation of the lid-moving cylinder 108, the lid102 moves between a treatment position, at which the lid 102 covers atop opening of the treatment tank 100 and a retreat position beside thetreatment tank 100. In a surface (upper surface) of the lid 102, asdescribed below, there is provided a nozzle plate 112 having a largenumber of jet nozzles 112 a for jetting outwardly (upwardly), forexample, electrolytic ionic water having reducing power.

Further, as shown in FIG. 11, a nozzle plate 124 having a plurality ofjet nozzles 124 a, for jetting upwardly a liquid chemical supplied froma liquid chemical tank 120 by driving the liquid chemical pump 122, isprovided in the inner tank 100 b of the treatment tank 100 in such amanner that the jet nozzles 124 a are equally distributed over an entiresurface of a cross section of the inner tank 100 b. A drain pipe 126 fordraining a liquid chemical (waste liquid) to outside is connected to abottom of the inner tank 100 b. A three-way valve 128 is provided in thedrain pipe 126, and the liquid chemical (waste liquid) is returned tothe liquid chemical tank 120 through a return pipe 130 connected to oneof ports of the three-way valve 128 to recycle the liquid chemical, asneeded. Further, in this embodiment, the nozzle plate 112 provided onthe surface (upper surface) of the lid 102 is connected to a rinsingliquid supply source 132 for supplying a rinsing liquid such as purewater. Further, a drain pipe 127 is connected to a bottom of the outertank 100 a.

By lowering the processing head 60 holding the substrate so as to coveror close the top opening of the treatment tank 100 with the processinghead 60, and then jetting a liquid chemical from the jet nozzles 124 aof the nozzle plate 124 disposed in the treatment tank 100 toward thesubstrate W, the liquid chemical can be jetted uniformly onto an entirelower surface (processing surface) of the substrate W and the liquidchemical can be discharged from the discharge pipe 126 while preventingscattering of the liquid chemical to the outside. Further, by raisingthe processing head 60 and closing the top opening of the treatment tank100 with the lid 102, and then jetting a rinsing liquid from the jetnozzles 112 a of the nozzle plate 112 disposed in the upper surface ofthe lid 102 toward the substrate W held in the processing head 60, arinsing treatment (cleaning treatment) is performed to remove the liquidchemical from the surface of the substrate. Because the rinsing liquidpasses through a clearance between the outer tank 100 a and the innertank 100 b and is discharged through the drain pipe 127, the rinsingliquid is prevented from flowing into the inner tank 100 b and frombeing mixed with the liquid chemical.

According to the pre-treatment apparatus 18 or 20, the substrate W isinserted into the processing head 60 and held therein when theprocessing head 60 is in a raised position, as shown in FIG. 5.Thereafter, as shown in FIG. 6, the processing head 60 is lowered to aposition at which it covers the top opening of the treatment tank 100.While rotating the processing head 60 and thereby rotating the substrateW held in the processing head 60, a liquid chemical is jetted from thejet nozzles 124 a of the nozzle plate 124 disposed in the treatment tank100 toward the substrate W, thereby jetting the liquid chemicaluniformly onto an entire surface of the substrate W. The processing head60 is raised and stopped at a predetermined position and, as shown inFIG. 7, the lid 102 in a retreat position is moved to a position atwhich it covers the top opening of the inner tank 100 b of the treatmenttank 100. A rinsing liquid is then jetted from the jet nozzles 112 a ofthe nozzle plate 112 disposed in the upper surface of the lid 102 towardthe rotating substrate W held in the processing head 60. A chemicaltreatment with the liquid chemical and a rinsing treatment with therinsing liquid of the substrate W can thus be performed successivelywhile avoiding mixing of these two liquids.

A lowermost position of the processing head 60 may be adjusted to adjusta distance between the substrate W held in the processing head 60 andthe nozzle plate 124, whereby a region of the substrate W onto which theliquid chemical is jetted from the jet nozzles 124 a of the nozzle plate124 and a jetting pressure can be adjusted as desired. Here, when apre-treatment liquid such as a liquid chemical is circulated and reused,active components are reduced by progress of the treatment, and thepre-treatment liquid (liquid chemical) is taken out due to attachment ofthe treatment liquid to the substrate. Therefore, it is desirable toprovide a pre-treatment liquid management unit (not shown) for analyzingcomposition of the pre-treatment liquid and adding insufficientcomponents.

FIGS. 12 through 18 show an electroless plating unit 22. Thiselectroless plating unit 22 includes a plating tank 200 (see FIG. 18)and a substrate head 204, disposed above the plating tank 200, fordetachably holding a substrate W.

As shown in detail in FIG. 12, the processing head 204 has a housing 230and a head portion 232. The head portion 232 mainly comprises a suctionhead 234 and a substrate receiver 236 for surrounding the suction head234. The housing 230 accommodates therein a substrate rotating motor 238and substrate receiver drive cylinders 240. The substrate rotating motor238 has an output shaft (hollow shaft) 242 having an upper end coupledto a rotary joint 244 and a lower end coupled to the suction head 234 ofthe head portion 232. The substrate receiver drive cylinders 240 haverespective rods coupled to the substrate receiver 236 of the headportion 232. Stoppers 246 are provided in the housing 230 formechanically limiting upward movement of the substrate receiver 236.

The suction head 234 and the substrate receiver 236 are operativelyconnected to each other by a splined structure such that when thesubstrate receiver drive cylinders 240 are actuated, the substratereceiver 236 vertically moves relative to the suction head 234, and whenthe substrate rotating motor 238 is driven, the output shaft 242 thereofis rotated to rotate the suction head 234 and the substrate receiver 236in unison with each other.

As shown in detail in FIGS. 13 through 15, a suction ring 250 forattracting and holding a substrate W against its lower surface to besealed is mounted on a lower circumferential edge of the suction head234 by a presser ring 251. The suction ring 250 has a recess 250 acontinuously defined in a lower surface thereof in a circumferentialdirection and in communication with a vacuum line 252 extending throughthe suction head 234 by a communication hole 250 b that is defined inthe suction ring 250. When the recess 250 a is evacuated, the substrateW is attracted to and held by the suction ring 250. Because thesubstrate W is attracted under vacuum to the suction ring 250 along aradially narrow circumferential area provided by the recess 250 a, anyadverse effects such as flexing caused by the vacuum on the substrate Ware minimized. When the suction ring 250 is dipped in a plating solution(treatment liquid), not only the surface (lower surface) of thesubstrate W, but also its circumferential edge, can be dipped into theplating solution. The substrate W is released from the suction ring 250by introducing N₂ into the vacuum line 252.

The substrate receiver 236 is in the form of a downwardly open, hollowbottomed cylinder having substrate insertion windows 236 a defined in acircumferential wall thereof for inserting therethrough the substrate Winto the substrate receiver 236. The substrate receiver 236 also has anannular ledge 254 projecting inwardly from its lower end, andprotrusions 256 disposed on an upper surface of the annular ledge 254and having a tapered inner circumferential surface 256 a for guiding thesubstrate W.

As shown in FIG. 13, when the substrate receiver 236 is lowered, thesubstrate W is inserted through the substrate insertion window 236 ainto the substrate receiver 236. The substrate W thus inserted is guidedby the tapered surfaces 256 a of the protrusions 256 and positionedthereby onto the upper surface of the ledge 254 in a predeterminedposition thereon. The substrate receiver 236 is then elevated until itbrings the upper surface of the substrate W placed on the ledge 254 intoabutment with the suction ring 250 of the suction head 234, as shown inFIG. 14. Then, the recess 250 a in the vacuum ring 250 is evacuatedthrough the vacuum line 252 to attract the substrate W while sealing anupper peripheral edge surface of the substrate W against a lower surfaceof the suction ring 250. In order to plate the substrate W, as shown inFIG. 15, the substrate receiver 236 is lowered several mm to space thesubstrate W from the ledge 254, keeping the substrate W attracted onlyby the suction ring 250. The substrate W now has its lower peripheraledge surface prevented from not being plated because it is held out ofcontact with the ledge 254.

FIG. 16 shows details of the plating tank 200. The plating tank 200 isconnected at a bottom thereof to a plating solution supply pipe 308 (seeFIG. 18), and is provided in a peripheral wall thereof with a platingsolution recovery groove 260. In the plating tank 200, there aredisposed two current plates 262, 264 for stabilizing flow of a platingsolution flowing upward. A thermometer 266 for measuring a temperatureof plating solution introduced into the plating tank 200 is disposed atthe bottom of the plating tank 200. Further, on an outer surface of aperipheral wall of the plating tank 200 and at a position slightlyhigher than a liquid level of the plating solution held in the platingtank 200, there is provided a jet nozzle 268 for jetting a stop liquidwhich is a neutral liquid having a pH of 6 to 7.5, for example, purewater, inwardly and slightly upwardly in a normal direction. Afterplating, the substrate W held in the head portion 232 is raised andstopped at a position slightly above a surface of the plating solution.In this state, pure water (stop liquid) is immediately jetted from thejet nozzle 268 toward the substrate W to cool the substrate W, therebypreventing progress of plating by the plating solution remaining on thesubstrate W.

Further, at a top opening of the plating tank 200, there is provided aplating tank cover 270 which closes the top opening of the plating tank200 during a non-plating time, such as idling time, so as to preventunnecessary evaporation of plating solution from the plating tank 200.

As shown in FIG. 18, a plating solution supply pipe 308, extending froma plating solution storage tank 302 and having a plating solution supplypump 304 and a three-way valve 306, is connected to the plating tank 200at the bottom of the plating tank 200. With this arrangement, during aplating process, a plating solution is supplied into the plating tank200 from the bottom of the plating tank 200, and overflowing platingsolution is recovered by the plating solution storage tank 302 through aplating solution recovery groove 260. Thus, the plating solution can becirculated. A plating solution return pipe 312 for returning the platingsolution to the plating solution storage tank 302 is connected to one ofports of the three-way valve 306. Thus, the plating solution can becirculated even in a standby condition of plating, and a platingsolution circulating system is constructed. As described above, theplating solution in the plating solution storage tank 302 is alwayscirculated through the plating solution circulating system, and hence alowering rate of concentration of the plating solution can be reducedand a number of substrates W which can be processed can be increased,compared with a case in which the plating solution is simply stored.

Particularly, in this embodiment, by controlling the plating solutionsupply pump 304, a flow rate of the plating solution which is circulatedat a standby of plating or at a plating process can be set individually.Specifically, an amount of circulating plating solution at the standbyof plating is in the range of 2 to 20 liter/minute, for example, and anamount of circulating plating solution during a plating process is inthe range of 0 to 10 liter/minute, for example. With this arrangement, alarge amount of circulating plating solution during standby of platingcan be ensured to keep a temperature of a plating bath in the cellconstant, and the flow rate of the circulating plating solution is madesmaller during the plating process to form a coating film (plated film)having a more uniform thickness.

The thermometer 266 provided in the vicinity of the bottom of theplating tank 200 measures a temperature of the plating solutionintroduced into the plating tank 200, and controls a heater 316 and aflow meter 318 described below.

Specifically, in this embodiment, there are provided a heating device322 for heating the plating solution indirectly by a heat exchanger 320which is provided in the plating solution in the plating solutionstorage tank 302 and uses water as a heating medium which has beenheated by a separate heater 316 and has passed through the flow meter318, and a stirring pump 324 for mixing the plating solution bycirculating the plating solution in the plating solution storage tank302. This is because during electroless plating, in some cases, theplating solution is used at a high temperature (about 80° C.), and thisstructure should cope with such cases. This method can prevent verydelicate plating solution from being mixed with foreign matter or thelike, unlike an in-line heating method.

FIG. 17 shows details of a cleaning tank 202 provided beside the platingtank 200. At a bottom of the cleaning tank 202, there is provided anozzle plate 282 having a plurality of jet nozzles 280, attachedthereto, for upwardly jetting a rinsing liquid such as pure water. Thenozzle plate 282 is coupled to an upper end of a nozzle lifting shaft284. The nozzle lifting shaft 284 can be moved vertically by changing aposition of engagement between a nozzle position adjustment screw 287and a nut 288 engaging the screw 287 so as to optimize a distancebetween the jet nozzles 280 and a substrate W disposed above the jetnozzles 280.

Further, on an outer surface of a peripheral wall of the cleaning tank202 and at a position above the jet nozzles 280, there is provided ahead cleaning nozzle 286 for jetting a cleaning liquid, such as purewater, inwardly and slightly downwardly onto at least a portion, whichwas in contact with the plating solution, of the head portion 232 of thesubstrate head 204.

In operating the cleaning tank 202, the substrate W held in the headportion 232 of the substrate head 204 is located at a predeterminedposition in the cleaning tank 202. A cleaning liquid (rinsing liquid),such as pure water, is jetted from the jet nozzles 280 to clean (rinse)the substrate W, and at the same time, a cleaning liquid such as purewater is jetted from the head cleaning nozzle 286 to clean at least aportion, which was in contact with the plating solution, of the headportion 232 of the substrate head 204, thereby preventing a deposit fromaccumulating on that portion which was immersed in the plating solution.

According to this electroless plating apparatus 22, when the substratehead 204 is in a raised position, the substrate W is held by vacuumattraction in the head portion 232 of the substrate head 204 asdescribed above, while the plating solution in the plating tank 200 isallowed to circulate.

When plating is performed, the plating tank cover 270 is opened, and thesubstrate head 204 is lowered, while the substrate head 204 is rotating,so that the substrate W held in the head portion 232 is immersed in theplating solution in the plating tank 200.

After immersing the substrate W in the plating solution for apredetermined time, the substrate head 204 is raised to lift thesubstrate W from the plating solution in the plating tank 200 and, asneeded, pure water (stop liquid) is immediately jetted from the jetnozzle 268 toward the substrate W to cool the substrate W, as describedabove. The substrate head 204 is further raised to lift the substrate Wto a position above the plating tank 200, and rotation of the substratehead 204 is stopped.

Next, while the substrate W is held by vacuum attraction in the headportion 232 of the substrate head 204, the substrate head 204 is movedto a position right above the cleaning tank 202. While rotating thesubstrate head 204, the substrate head 204 is lowered to a predeterminedposition in the cleaning tank 202. A cleaning liquid (rinsing liquid),such as pure water, is jetted from the jet nozzles 280 to clean (rinse)the substrate W, and at the same time, a cleaning liquid such as purewater is jetted from the head cleaning nozzle 286 to clean at least aportion, which was in contact with the plating solution, of the headportion 232 of the substrate head 204.

After completion of cleaning of the substrate W, rotation of thesubstrate head 204 is stopped, and the substrate head 204 is raised tolift the substrate W to a position above the cleaning tank 202. Further,the substrate head 204 is moved to a transfer position between thetransport robot 34 and the substrate head 204, and the substrate W istransferred to the transport robot 34, and is transported to a nextprocess by the transport robot 34.

As shown in FIG. 18, the electroless plating apparatus 22 is providedwith a plating solution management unit 330 for measuring an amount ofplating solution held by the electroless plating apparatus 22 and foranalyzing composition of the plating solution by an absorptiometricmethod, a titration method, an electrochemical measurement, or the like,thereby replenishing components which are insufficient in the platingsolution. In the plating solution management unit 330, signalsindicative of analysis results are processed to replenish insufficientcomponents from a replenishment tank (not shown) to the plating solutionstorage tank 302 using a metering pump, thereby controlling an amount ofthe plating solution and composition of the plating solution. Thus, thinfilm plating can be realized with good reproducibility.

The plating solution management unit 330 has a dissolved oxygendensitometer 332 for measuring dissolved oxygen in the plating solutionheld by the electroless plating apparatus 22 by an electrochemicalmethod, for example. According to the plating solution management unit330, dissolved oxygen concentration in the plating solution can becontrolled at a constant value on the basis of indication of thedissolved oxygen densitometer 332 by deaeration, nitrogen blowing, orother methods. In this manner, a dissolved oxygen concentration in theplating solution can be controlled at a constant value, and the platingreaction can be achieved with good reproducibility.

FIGS. 19 and 20 show a post-treatment/drying unit 400, which is usedboth as post-treaement unit 24 and the drying unit 26 shown in FIG. 3,for performing post-treating of a substrate and drying continuously.Specifically, the post-treatment/drying unit 400 performs chemicalcleaning (post-treatment) and pure water cleaning (rinsing) first, andthen complete drying of the substrate W which has been cleaned byspindle rotation. The post-treatment/drying unit 400 comprises asubstrate stage 422 having a clamp mechanism 420 for clamping an edgeportion of the substrate W, and a substrate mounting and removinglifting/lowering plate 424 for opening and closing the clamp mechanism420.

The substrate stage 422 is coupled to an upper end of a spindle 426 thatis rotated at a high speed by energization of a spindle rotating motor(not shown). Further, a cleaning cup 428 for preventing a treatmentliquid from being scattered around is disposed around the substrate Wheld by the clamp mechanism 420, and the cleaning cup 428 is verticallymoved by actuation of a cylinder (not shown).

Further, the post-treatment/drying unit 400 comprises a liquid chemicalnozzle 430 for supplying a treatment liquid to the surface of thesubstrate W held by the clamp mechanism 420, a plurality of pure waternozzles 432 for supplying pure water to a backside surface of thesubstrate W, and a pencil-type cleaning sponge 434 which is disposedabove the substrate W held by the clamp mechanism 420 and is rotatable.The pencil-type cleaning sponge 434 is attached to a free end of a swingarm 436 which is swingable in a horizontal direction. Clean airintroduction ports 438 for introducing clean air into the apparatus areprovided at an upper part of the post-treatment/drying unit 400.

With the post-treatment/drying unit 400 having the above structure, thesubstrate W is held and rotated by the clamp mechanism 420, and whilethe swing arm 436 is swung, a treatment liquid is supplied from theliquid chemical nozzle 430 to the cleaning sponge 434, and the surfaceof the substrate W is rubbed with the pencil-type cleaning sponge 434,thereby post-treating the surface of the substrate W. Further, purewater is supplied to the backside surface of the substrate W from thepure water nozzles 432, and the backside surface of the substrate W issimultaneously cleaned (rinsed) by pure water ejected from the purewater nozzles 432. Thus cleaned substrate W is spin-dried by rotatingthe spindle 426 at a high speed.

According to this embodiment, optical sensors that are orientable to anyposition on a substrate are used as the film thickness sensor 30 a andthe film property sensor 30 b provided in the measurement unit 30. Eachoptical sensor may be one that utilizes spectroreflectometry,ellipsometry or spectroscopic ellipsometry using ultraviolet rays. Withsuch an optical sensor, measurement can be performed in anon-destructive manner, i.e. without destroying a substrate, and in ashort time of about several seconds to several tens of seconds for onemeasurement area. This is desirable in light of quality control. It isalso possible to use an optical sensor which utilizes X-ray reflectance,grazing-incidence fluorescent X-rays or a plurality of laserinterferometers. Such an optical sensor enables real-time measurement ofa change in film properties of a film being processed (measurementobject) in air or in a liquid.

When such an optical sensor is used as the film thickness sensor 30 aand the film property sensor 30 b, a spot size of a sensor beam, afternarrowing the beam, is generally from several μm to several tens of μm.On the other hand, when selectively covering exposed surfaces ofinterconnects 8 with a coating film (protective film) 9, as shown inFIG. 1, device performance is primarily governed by the coating film 9formed on the interconnects 8. Accordingly, it is most important tocontrol properties of the coating film 9 formed on the interconnects 8.However, width B of the interconnects 8 is generally not more than 1 μm(e.g. 0.16 μm) . Accordingly, when attempting to directly measure a filmthickness or properties of the coating film 9 formed on theinterconnects 8 shown in FIG. 1, this measurement is influenced by anadjacent insulating film (insulating material) 2 whose surface isexposed. This will produce a large measurement error and, in some cases,make the measurement impossible.

According to this embodiment, as shown in FIGS. 21A and 21B, ameasurement area P, which has a larger size than spot size S of anarrowed sensor beam of an optical sensor and on which a continuous filmis to be formed, and a target area M as a control target are set(selected) within a region defining one clip C in a substrate W, such asa semiconductor wafer. A film thickness of the coating film 9 in themeasurement area P is measured with the film thickness sensor 30 a,which is an optical sensor, and a film property is measured with thefilm property sensor 30 b, which is also an optical sensor, and, basedon these measured values, the film thickness and the film property ofthe coating film 9 in the control target area M, which has a smallersize than the spot size S, are determined.

In particular, with respect to film thickness, film thicknesses of thecoating film 9 in the measurement area P and in the target area M aremeasured, for example, by using a destructive measuring method such asTEM (transmission electron microscope), to thereby prepare a calibrationcurve showing a relationship between the film thickness of the coatingfilm 9 in the measurement area P and that in the target area M, as shownin FIG. 22. A measured film thickness, which is measured in themeasurement area P with the film thickness sensor 30 a, is converted tothe film thickness in target area M by using the calibration curve. Thefilm thickness of the coating film 9 in the target area M can thus bedetermined in an indirect manner.

Also with film properties, as shown in 23, a calibration curve showing arelationship between a film property of the coating film 9 in themeasurement area P and that in the target area M is prepared using, forexample, a destructive method such as TEM. A measured film property,which is measured in measurement area P with the film property sensor 30b, is converted to the film property in target area M by using thecalibration curve. The film property of the coating film 9 in targetarea M can thus be determined in an indirect manner. The film propertyto be measured is, for example, film composition, density, refractiveindex, surface roughness, reflectance, or interface width.

In this manner, a film thickness and film properties of a film formed ona substrate can be measured without being influenced by an insulatingfilm (insulating material), and based on results of this measurement, afilm thickness and film properties of a coating film formed oninterconnects, whose measurement is generally impossible, can bedetermined indirectly via a calibration curve.

A film-forming region larger than the spot size S of the narrowedoptical beam of an optical sensor can be utilized as a measurement areaP on which film thickness and film properties are measurable, if such aregion is present on a substrate. If there is no such region, it can bedealt with by making a dummy pattern in a desired region on a substrate.

A description will now be given of a series of electroless platingprocessings, whose flow chart is shown in FIG. 4, performed by thesubstrate processing apparatus. The following description illustrates acase of selectively forming a coating film (protective film) 9 of aCo—W—P alloy to protect interconnects 8, as shown in FIG. 1.

First, one substrate W is taken by the transport robot 34 out of thecassette 10, set in the loading/unloading unit 12 and housing substratesW, with its front surface facing upwardly (face up), with each substrateW having been subjected to formation of interconnects 8 in surfacesfollowed by drying, and the substrate W is transported to the firstpre-treatment unit 18. In the first pre-treatment unit 18, the substrateW is held face down, and cleaning treatment (chemical cleaning) as apre-plating treatment is performed on a front surface. For example, aliquid chemical, such as dilute H₂SO₄, at a liquid temperature of e.g.25° C. is jetted toward the surface of the substrate W to thereby removeCMP residues, such as copper, remaining on a surface of insulating film2 (see FIG. 1), or an oxide on the interconnects. Thereafter, thecleaning chemical remaining on the surface of the substrate W is rinsed(cleaned) off with a rinsing liquid, such as pure water.

Liquid chemicals for use in this pre-treatment include an inorganic acidwith a pH of not more than 2, such as hydrofluoric acid, sulfuric acidor hydrochloric acid; an acid with a pH of not more than 5 and havingchelating ability, such as formic acid, acetic acid, oxalic acid,tartaric acid, citric acid, maleic acid or salicylic acid; and an acidwith a pH of not more than 5 to which is added a chelating agent such asa halide, a carboxylic acid, a dicarboxylic acid, an oxycarboxylic acid,or a water-soluble salt thereof. By performing cleaning of the substratewith such a chemical, CMP residues, such as copper, remaining on theinsulating film and an oxide on the surface of interconnects can beremoved, whereby plating selectivity and adhesion of a plating tounderlying material, i.e. the interconnects, can be enhanced. Ananticorrosive agent, which is generally used in CMP, usually acts as aninhibitor against deposition of a plating film. Such an anticorrosiveagent can be effectively removed by using an alkali chemical capable ofremoving an anticorrosive agent adhering to interconnects, for example,tetramethylammonium hydroxide (TMAH). The same effect as produced by theabove-described acids can also be produced by an alkaline solution of anamino acid, such as glycine, cysteine, methionine, and the like.

Rinsing (cleaning) with a rinsing liquid of the surface of the substrateW after cleaning can prevent a chemical used in cleaning from remainingon the surface of the substrate W and impeding a next activation step.Ultrapure water is generally used as a rinsing liquid. Depending upon amaterial of the to-be-plated surface, however, an interconnect materialcan corrode, for example, due to local cell effect even when ultrapurewater is used. It is desirable, in such a case, to use as a rinsingliquid water containing no impurity and having high reducing powder,such as hydrogen gas-dissolved water obtained by dissolving hydrogen gasin ultrapure water, or electrolytic cathode water obtained by subjectingultrapure water to diaphragm-type electrolysis. In order to preventpossible corrosion of interconnect material, and the like, by thechemical used in cleaning, a time between cleaning and rinsing ispreferably as short as possible.

Next, the substrate W after cleaning and rinsing is transported by thetransport robot 34 to the second pre-treatment unit 20, where thesurface of the substrate W is subjected to a catalyst impartationtreatment while it is held face down. For example, a mixed solution ofPdCl₂/HCl at a liquid temperature of 25° C. is jetted toward the surfaceof the substrate W to thereby attach Pd as a catalyst to the surface ofinterconnects 8, i.e., form Pd nuclei as catalyst nuclei in surfaces ofinterconnects 8, thereby activating exposed surfaces of interconnects 8.Thereafter, the catalyst-containing liquid chemical remaining on thesurface of the substrate W is rinsed (cleaned) off with a rinsingliquid, such as pure water.

An inorganic or organic solution containing Pd is used as the liquidchemical (catalyst-containing liquid). If the Pd content of thecatalyst-containing liquid is too low, a catalyst density in theto-be-plated surface is so low that plating cannot be effected. Too higha Pd content will cause defects, such as formation of pits, in theinterconnects 8.

In order to form a uniform and continuous electroless plating film overan entire surface of the substrate, a catalyst must be imparted to ato-be-plated surface at least in a certain amount. It has been confirmedexperimentally that when using palladium as a catalyst, that certainamount (minimum amount) is 0.4 μg per 1 cm² of the to-be-plated surface.It is known that impartation of Pd in a high amount causes corrosion ofthe to-be-plated material and increases resistivity of thiscatalyst-imparted material. It has also been confirmed that thisphenomenon is marked when palladium is imparted in an amount of 8 μg ormore per 1 cm² of the to-be-plated surface. This impartation of thecatalyst to the surface of the substrate W can enhance selectivity ofelectroless plating.

Further, in order to enhance the selectivity, it is necessary to removePd remaining on the insulating film 2 and on the interconnects 8. Tothis end, pure water rinsing is generally employed. As with the case ofthe cleaning treatment, the catalyst-containing liquid remaining on thesubstrate surface can exert adverse influence on the interconnects, suchas corrosion, and on the plating step. It is therefore desirable that atime between the catalyst impartation treatment and rinsing be as shortas possible. As with the case of the cleaning treatment, pure water,hydrogen gas-dissolved water or electrolytic cathode water may be usedas a rinsing liquid. Alternatively, in order to make the substratesurface better adapted to an electroless plating solution which is usedin a next plating step, it is also possible to use an aqueous solutionof a component(s) composed of the electroless plating solution.

The substrate W after the catalyst impartation treatment and rinsing istransported by the transport robot 34 to the electroless plating unit22, where electroless plating of the surface of the substrate W isperformed while it is held face down. For example, the substrate W isimmersed in a Co—W—P plating solution at a liquid temperature of 80° C.,for example, for about 120 seconds to perform selective electrolessplating (electroless Co—W—P cap plating) on activated surfaces ofinterconnects 8, thereby selectively forming a coating film (protectivefilm) 9. The plating solution has, for example, the followingcomposition:

CoSO₄.7H₂O: 14 g/L

-   -   Na₃C₆H₅O₇.2H₂O: 70 g/L    -   H₃BO₃: 40 g/L    -   Na₂WO₄.2H₂O: 12 g/L    -   NaH₂PO₂.H₂O: 21 g/L    -   pH: 9.5

A film formation rate of coating film 9 during electroless plating ispreferably 10 to 200 Å per minute. Since a plating rate directly affectsproductivity, a low plating rate is generally undesirable. Too high aplating rate, however, cannot ensure uniformity and reproducibility ofplating. The coating film 9 is often required to have a film thicknesson the order of several tens of Å to several hundred Å. The plating rate(film formation rate) of 10 to 200 Å per minute is desirable to form thecoating film 9 having such a film thickness. The plating rate can becontrolled by both compositional conditions of the plating solution,such as pH, and reaction conditions, such as a reaction temperature.

The plating solution preferably contains W at a concentration of atleast 1.5 g/L. In order for a plated Ni alloy or Co alloy to fullyfunction as a coating film 9, this alloy film desirably contains aneffective amount of W. In that case, the plating solution must contain Win a certain amount. By making the certain amount at least 1.5 g/L, theW content of the alloy can be controlled at an effective level.

As in this embodiment, the coating film 9 is preferably composed of analloy comprising the three elements, Co, W and P. This is because amongNi alloys and Co alloys, an alloy comprising the three elements Co, Wand P is relatively slow in its film formation rate, which isadvantageous to formation of a thin film. In addition, the platingsolution is relatively stable, thereby enabling easy control andreproduction of the film composition.

After raising the substrate W from the plating solution, a stop liquid,which is a neutral liquid having a pH of 6 to 7.5, is brought intocontact with the surface of the substrate W, thereby stoppingelectroless plating. By thus stopping a plating reaction promptly afterraising the substrate W from the plating solution, a plated film can beprevented from becoming uneven. A time for the treatment with the stopliquid is preferably from 1 to 5 seconds. The stop liquid may beexemplified by pure water, hydrogen gas-dissolved water and electrolyticcathode water. As described above, the interconnect material can corrodedue to local cell effect. Such a problem can be avoided by stoppingplating with ultrapure water which is made reductive.

Thereafter, the plating solution remaining on the surface of thesubstrate is rinsed (cleaned) off with a rinsing liquid, such as purewater. The coating film (protective film) 9 of Co—W—P alloy is thusformed selectively on the surfaces of interconnects 8 to protect theinterconnects 8.

Next, the substrate W is transported by the transport robot 34 to thepost-treatment unit 24, where the substrate is subjected topost-treatment to enhance selectivity of the coating film (plating film)9 formed on the surfaces of the substrate W, thereby enhancing yield. Inparticular, while applying a physical force to the surface of thesubstrate W, for example, by performing roll scrub cleaning or pencilcleaning, a liquid chemical containing one or more of a surfactant, anorganic alkali and a chelating agent is supplied to the surface of thesubstrate W to thereby completely remove plating residues, such as finemetal particles, on the insulating film 2, thus enhancing selectivity ofplating. Use of such a liquid chemical can more effectively enhanceselectivity of electroless plating. The surfactant is preferably anonionic one, the organic alkali is preferably a quaternary ammoniumcompound or an amine, and the chelating agent is preferablyethylenediamine or its derivative.

When such a liquid chemical is employed, the chemical remaining on thesurface of the substrate W is rinsed (cleaned) off with a rinsingliquid, such as pure water. The rinsing liquid may be exemplified bypure water, hydrogen gas-dissolved water and electrolytic cathode water.As described above, the interconnect material can corrode due to a localcell effect. Such a problem can be avoided by performing rinsing of thesubstrate with ultrapure water which is made reductive.

Besides the above-described roll scrub cleaning or pencil cleaning whicheffects cleaning through a physical force, it is also possible to employcleaning with a complexing agent, uniform etching back with an etchingliquid, and the like, or a combination thereof to completely removeplating residues remaining on the insulating film.

The substrate W after this post-treatment is transported by thetransport robot 34 to the drying unit 26, where the substrate W isrinsed, according to necessity, and is then spin-dried by rotating it ata high speed.

The substrate W after spin-drying is transported by the transport robot34 to the heat treatment unit 28, where the substrate W after thepost-treatment is subjected to heat treatment (annealing) formodification of the coating film 9. Taking account of a practicalprocessing time, a temperature necessary for modification of the coatingfilm 9 is at least 120° C. Also taking account of heat resistance ofmaterials constituting devices, a heating temperature is desirably nothigher than 450° C. Accordingly, a temperature for heat treatment(annealing) is, for example, 120 to 450° C. By thus heat treating thesubstrate W, barrier properties of a coating film (plated film) formedon exposed surfaces of interconnects, and its adhesion to theinterconnects, can be improved.

Next, the substrate W after the electroless plating and the heattreatment is transported by the transport robot 34 to the measurementunit 30. A film thickness and a film property(ies) of the coating film 9in a measurement area P of the substrate W are measured by the filmthickness sensor 30 a and the film property sensor 30 b provided in themeasurement unit 30, respectively. These measured values are convertedto the film thickness and the film property of the coating film 9 in atarget area M by using calibration curves as shown in FIGS. 22 and 23,thus indirectly determining the film thickness and the film property inthe target area M.

Results of an off-line measurement of the film thickness and filmproperty of the coating film 9 formed on the exposed surfaces ofinterconnects 8 are fed back prior to electroless plating of a nextsubstrate. Thus, based on the film thickness and the film property thusdetermined, a processing time for plating of the next substrate or acomposition of a liquid chemical, for example, is adjusted. In thismanner, the film thickness and film properties of the coating film 9formed on the exposed surfaces of interconnects 8 can be controlled atconstant values.

By thus measuring and controlling the film thickness and film propertiesof the coating film 9 after film formation, it becomes possible toensure quality of the film and obtain a stable product even when thecoating film is in the form a number of separate discontinuous filmswhose properties are likely to vary.

Next, the substrate W after this measurement is returned by thetransport robot 34 to the substrate cassette 10 set in theloading/unloading unit 12.

Though in this embodiment a Co—W—P alloy film is used as the coatingfilm 9, it is also possible to use a coating film composed of a Co—P,Ni—P, Ni—W—P, Co—B or Co—W—B alloy. Further, though copper is used as aninterconnect material, it is also possible to use a copper alloy,silver, a silver alloy, gold, a gold alloy, or the like.

Though in this embodiment the film thickness and a film property(ies) ofthe coating film 9 (see FIG. 1) immediately after its formation in theelectroless plating unit 22 are measured with the film thickness sensor30 a and the film property sensor 30 b, both provided in the measurementunit 30, it is also possible to provide the film thickness sensor 30 aand the film property sensor 30 b on an inner surface of the platingtank 200 of the electroless plating unit 22, as shown in FIG. 16, andmeasure the film thickness and a film property of the coating film 9 inreal time during film formation with the film thickness sensor 30 a andthe film property sensor 30 b.

Further, though in this embodiment the measurement unit 30 is installedin the rectangular housing 16, the measurement unit 30 may be installedin a special space outside the housing 16.

It is, of course, possible to directly measure a film thickness and afilm property at a desired position on a substrate. In this case, aparticular area at the same position on each substrate may be set as acontrol target, and a film thickness and a film property in theparticular area may be measured and controlled. This effectivelyprevents quality variations between substrates. It is also possible toset a plurality of areas on a substrate as control targets, andsimultaneously or sequentially measure and control film thicknesses andfilm properties in this plurality of measurement areas. This can preventquality variations in the substrate.

The present invention has been described above with reference to thecase of measuring and controlling film thickness and/or film propertiesof the coating film 9 shown in FIG. 1 upon its formation in theelectroless plating apparatus. Though not shown diagrammatically, thepresent invention is also applicable to a substrate processing apparatusincluding: an etching unit for etching a substrate having a metal and aninsulating material exposed on its surface in such a manner that anexposed surface of the metal is selectively removed; a sensor formeasuring a decrease in film thickness of a metal portion during and/orimmediately after removal processing of the metal portion; and a controlsection for controlling the etching unit based on an output from thesensor. According to this apparatus, as shown in FIG. 2, whenselectively etching and removing top portions of interconnects 8 by theetching unit to form recesses 8 a preparatory to forming the coatingfilm 9 such that its surface becomes flush with a surface of theinsulating film 2, depth d of the recesses 8 a is measured with thesensor. The control section controls the etching unit based on an outputfrom the sensor so as to control the depth of the recesses 8 a.

The present invention is also applicable to a substrate processingapparatus including: a polishing unit for polishing a substrate having ametal and an insulating material exposed on its surface in such a mannerthat an exposed surface of the metal is selectively removed; a sensorfor measuring a decrease in film thickness of a metal portion duringand/or immediately after removal processing of the metal portion; and acontrol section for controlling the polishing unit based on an outputfrom the sensor. According to this apparatus, depth d of the recesses 8a shown in FIG. 2 can be controlled in the manner as in the precedingembodiment.

As described hereinabove, according to the present invention, a filmthickness and/or film properties of a coating film are measured duringand/or immediately after formation of the coating film, and a filmthickness and/or film properties of a coating film is controlled. Thisensures quality of this film and makes it possible to provide a stableproduct even when the film is in the form a number of separatediscontinuous films whose properties are likely to vary. Further, byconverting a measured film thickness or film property value of aprocessed film, measured in a measurement area, to a film thickness orfilm property of a processed film in a target area by using a preparedcalibration curve, it becomes possible to indirectly determine the filmthickness or film property of the processed film if the film is one thatis formed on interconnects, whose measurement is generally impossible.

1-18. (canceled)
 19. A substrate processing apparatus comprising: aplating unit for plating a substrate with a metal and an insulatingmaterial exposed on its surface in such a manner that a coating film isformed selectively on the exposed surface of the metal; a sensor formeasuring the film thickness and/or a film property of the coating filmduring and/or immediately after formation of the coating film; and acontrol section for controlling the plating unit based on an output fromthe sensor. 20-21. (canceled)